The present invention relates generally to an exposure apparatus and method used to fabricate various devices including semiconductor chips such as ICs and LSIs, display devices such as liquid crystal panels, sensing devices such as magnetic heads, and image pick-up devices such as CCDs, as well as fine patterns used for micromechanics, and more particularly to an immersion type exposure method and apparatus that immerses the final surface of the projection optical system and the surface of the object in the fluid and exposes the object through the fluid.
A projection exposure apparatus has been conventionally used to transfer a circuit pattern on a reticle (or a mask) via a projection optical system onto a wafer etc, and the high-quality exposure at a high resolution has recently been increasingly demanded. The immersion exposure attracted people's attentions as one means that satisfies this demand. The immersion exposure promotes the higher numerical aperture (“NA”) by replacing a medium (typically the air) at the wafer side of the projection exposure with fluid. The projection exposure apparatus has an NA=n·sin θ where n is a refractive index of the medium, and the NA increases when the medium that has a refractive index higher than the air's refractive index, i.e., n>1.
For the immersion exposure, some methods have already been proposed to fill the fluid in the space between the object to be exposed, and the optical element in the projection optical system that is closest to the object. See, for example, International Publication No. WO99/49504, and International Symposium on 157 nm Lithography, 3-6 Sep. 2002, Belgium, Bruce Smith et al. (Rochester Institute of Technology), Extreme-NA Water Immersion Lithography for 35-65 nm Technology. These prior art references propose to provide, as shown in FIG. 15A, a supply nozzle 18 and a recovery nozzle 20 near a final lens 14 in the projection optical system, and supplies fluid 16 from the supply nozzle 18 between the substrate W and the final lens 14. In addition, an air curtain 22 is formed by blowing compressed air to the outside of the fluid 16 and maintains the fluid 16 between the substrate W and the final lens 14. Here, FIG. 15A is a schematic sectional view for explaining the fluid supply and recovery by a conventional immersion type exposure apparatus. Since an introduction of the fluid 16, an interval between the substrate W and the final lens 14 is maintained to be a necessary interval for exposure, and the exposure becomes immediately ready after the introduction. The exposure is performed, while the supply nozzle 18 continuously supplies the fluid 16 and the recovery nozzle 20 continuously recovers the fluid 16 or while the fluid 16 circulates between the substrate W and the final lens 14.
However, the conventional immersion exposure shown in FIG. 15A causes the air bubbles to mix the fluid, in filling the fluid 16 in the space between the substrate W and the final lens 14. The air bubble shields the exposure light, results in lowered transfer accuracy and yield, and cannot satisfy the demand for the high-quality exposure. The air bubbles are likely to generate at the initial filling of the fluid, i.e., when the fluid 16 is filled in a space between the substrate W and the final lens 14, which space contains no fluid 16. FIG. 15B shows this state, and is a plane view of FIG. 15A viewed from a direction A. As shown in FIG. 15B, surfaces of the substrate W and the final lens 14 have part 24 that is hydrophilic to the fluid 16, and part 26 that is less hydrophilic to the fluid 16. These parts 24 and 26 may be considered to be located on a front surface of the substrate W or a bottom surface final lens 14. As a result, the fluid 16 is recovered from the recovery nozzle 20 through the part 24. Then, the air that exists above the part 26 is not squeezed out by the fluid 16, and remains as air bubbles. These air bubbles would never be eliminated completely irrespective of the subsequent continuous supply and recovery of the fluid 16.